The present invention relates to fences for woodworking equipment and, more particularly, to fences for band saw fences that may be adjusted to compensate for drift introduced by the band saw blade.
Band saws basically comprise a table for supporting a workpiece and a blade formed by a thin metal band in the form of a closed loop and having teeth formed on one edge. The blade is supported on upper and lower rollers such that it extends through a hole in the table. The blade is displaced along its axis, and the workpiece is moved relative to the blade to form the cut. The use of a thin metal band allows the cut to follow a curved path. The inherent flexibility of a thin blade, however, makes band saws less appropriate for forming straight cuts.
Fences have long been used with band saws to help form straight cuts. The band saw defines a desired cutting plane that corresponds to a vertical plane extending through the blade at a right angle to the table. A band saw fence is fixed relative to table such that a fence surface is parallel to the desired cutting plane. The workpiece is held against the fence and moved relative to the blade to form the cut.
Depending upon a number of factors, the actual cutting plane of a band saw blade will often xe2x80x9cdriftxe2x80x9d at an angle that is offset from the desired cutting plane. This drift angle is generally consistent for a given machine under a given set of operating condition, but can change over time or if the operating conditions change.
With a conventional band saw fence, the drift of the blade will cause the cut to move towards or away from the fence. If the cut moves towards the fence, the distance between the cut and the edge of the workpiece adjacent to the fence will become smaller than desired, and the workpiece will tend to pull away from the fence. If the cut moves away from the fence, the distance between the cut and the edge of the workpiece adjacent to the fence will become larger than desired, and the workpiece will tend to bind between the fence and the blade. Both scenarios are unfavorable, and the need thus exists for a band saw fence that quickly easily adjusts to accommodate blade drift for different band saws and under different operating conditions.
The following references were uncovered during a professional patentability search conducted on behalf of the applicants.
Of the patents turned up in the search, only U.S. Pat. No. 3,508,590 to Sprague, Sr. is specifically designed for use with a band saw. While this patent discloses a guide member that is angularly adjustable relative to the saw blade, this guide member is intended to be moved relative to the workpiece to obtain a cross cut and not to form a stable surface for a rip cut. The Sprague, Sr. patent in no way recognizes the problem of blade drift, and the angular adjustment disclosed in this patent could in no way be used accommodate for such blade drift.
U.S. Pat. No. 2,064,607 to Hirtz, Sr. discloses a guide member for woodworking machines, including band saws. The guide member is angularly adjustable. This angular adjustment is described as either making the guide member parallel to the blade or to allow the guide member to function as a stop. This patent fails to recognize any problems specific to band saws, such as blade drift, and thus does not teach using angular adjustment offset such blade drift.
U.S. Pat. Nos. 381,752 and 575,709 to Beach and Drew disclose guide assemblies for table saws having two screws arranged on either side of a pivot point to adjust the angle of a guide member relative to a saw blade. These guide assemblies are not specifically designed for use on band saws. Further, the angular adjustment is designed to allow the guide member to be aligned with the saw blade and not to be offset to accommodate blade drift.
U.S. Pat. No. 2,710,633 to Oberg discloses a miter gauge for a table saw that can also be used as a rip fence. The miter gauge allows angular adjustment, but this patent does not relate to band saws and does not disclose obtaining an offset angle to accommodate blade drift.
U.S. Pat. No. 4,911,048 to Osborne discloses a gauge for a sawmill that is adjustable relative to a rotary saw blade. Again, this patent does not relate to band saws and could not disclose, teach, or suggest the use of an offset angle to accommodate blade drift.
The present invention may be embodied as a fence system for a band saw. The band saw defines an actual cutting plane and has a table having a table surface defining a desired cutting plane. The fence system comprises a rail member, a base member, a locking assembly, a fence member defining a fence surface, and an adjustment system.
The rail member is mounted on the table and defines a rail axis that is substantially perpendicular to the desired cutting plane. The base member is supported by the rail member. The locking assembly selectively locks the base member at a selected position along the rail axis. The adjustment system mounts the fence member to the base member at a selected angle relative to the rail axis. The base member defines a pivot point about which the fence member is rotated by the adjustment system, and the pivot point is adjacent to the rail member.
The present invention may also be embodied as a method of supporting a workpiece on a band saw to form a desired cut in a work piece. A rail member is mounted onto the table of the band saw. The rail member defines a rail axis that is substantially perpendicular to a desired cutting plane defined by the band saw. A base member is supported on the rail member. The base member is locked at a selected position along the rail axis. A fence member having a fence surface is mounted on the base member. The fence member is attached to the base member such that the fence member engages and rotates about a pivot point on the base member. First and second bolt assemblies are arranged on either side of the pivot point to attach the fence member to the base member at a selected angle relative to the rail axis. The workpiece is then moved relative to the band saw to form the desired cut.
Other configurations of the present invention are also novel, so the scope of the present invention should be determined based on the scope of the claims attached hereto and not this Summary of the Invention.